In most cases unfortunately yes. But Olds' new Turnpike Cruising Package option for their Cutlass Supreme Holiday Coupe proves, in the words of the Gershwin tune, that "It ain't necessarily so." Their engineers have seemingly untied the Gordian knot that allows good economy and performance in an American-sized passenger car.

This package consists of a high-compression 400-cubic-inch engine with a 2-barrel carburetor and special cam that moves the torque peak to a lower rpm than normal driving through a 2.41 rear axle. Also included is something particularly delightful, we think: the 4-4-2 suspension and chassis. A car thus equipped can be correctly considered a 4-4-2 (less identification) with a different engine and final drive ratio.

We made the obvious choice of a 4-4-2-with an almost identical list of accessories, including automatic transmission - as a companion test car for comparison. Other than engines and final drive, the only differences in equipment having any. effect on performance were tires and brakes. The 4-4-2 had F70-14 Wide-Ovals and front discs while the TC-equipped Cutlass had the standard 7.75 x 14 tires with drums. (The standard tires were later changed to UniRoyal Max 195R14 radial ply tires for evaluation.)

Although the 4-4-2 had the standardfor-automatic 3.08 rear axle, a fairly high-speed ratio, its engine sounded comparatively busy upon switching from the TC car with the 2.41 axle. At 65 mph the TC engine is churning over at a relaxed 2200 rpm while the 4-4-2 cranks out nearly 3000 at the same speed.

Without hesitation we rate the TC-packaged car above the 4-4-2 as an allaround road car for this reason. This goes for all kinds of roads -not just turnpikes - because with an identical suspension, it gives away nothing to the 4-4-2 in this department.

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Well, maybe it's tops in general roadability, but what about digging out and passing'? This is where even the car\vise, having merely read the specifications, might be tempted to dismiss the TC Setup as just the ticket for Mom and Dad or maybe Aunt Genevieve, but not for himself. Far from being a slug Our TC test car gave away only I second and 6 mph to the 4-4-2 in the quarter and hacked 0-60 in less than 9 seconds - performance not likely to bore anyone.

As can be seen from figures in the spec table, the real clincher for the TC package is the excellent gas mileage it gives, which favorably compares with that of smaller, less powerful V-8s and 6s installed in much lighter cars. A typical example of its performance in this respect versus the 4-4-2 is when we gassed up after driving both cars over the same stretch of highway for a distance of 213 miles at approximately 70 mph. The 4-4-2 took 16 gallons to fill while the TC car required only 13. Premium fuel (which the TC engine requires, too) happened to cost 42 cents a gallon at that particular location. So you can readily imagine the savings on an extended trip.

Olds hasn't made one available yet, but a lower-compression-ratio, regularfuel engine would make an attractive option. While not recording -quite so spectacular mileage figures, the 5- or 6- cheaper price of regular gasoline would permit a further 10 % cost saving.

A brief look at some of the technical factors involved might provide some insight as to why such a large engine in a fairly heavy car driving through a high-speed rear axle yields this kind of economy. Simply stated, such a combination reduces frictional and pumpin- losses, making more power available to drive the car. Frictional losses - the power required to turn the crank on its bearings, scrape of the piston rings against the cylinder bores, etc. - increase as the square of the rpm. This means that when rpm is reduced by one-half, the frictional loss is reduced to one-fourth its former value.

Much closer to the actual case of our two test cars would be where you reduce engine rpm from 2800 to 2000 but Still retain the same road speed by changing to a higher speed rear axle. This is onlv 800 rpm less, but you will have almost exactly halved the frictional power loss. Now you can see why relatively small decreases in engine rpm can result in large benefits.

Pumping losses stem from the useless work the pistons do pulling against the vacuum in the intake manifold. which increases both with increased rpm and higher vacuum. This vacuum is highest at high rpm and small throttle openings - the typical Situation for most cars at highway cruising speeds. In an almost utopian manner things start to resolve themselves in your favor when you go to a higher (lower numer- rear-axle ratio. First, there's less pumping loss simply because the engine's turning more slowly. Second, in order to maintain the former speed. the engine must produce more torque which requires a larger throttle opening which in turn further reduces the manifold vacuum. (The engine Must have the potential for increased torque, which is where the large engine comes in.) Thus you have two factors working to reduce pumping loss.

We could actually feel the difference in losses between the 4-4-2 Lind TC car by merely lifting off the accelerator at cruising speed. While the 4-4-2 had a strong deceleration from engine braking, the TC car felt almost as if it had shifted into neutral.

The TC car also had the Climatic Combustion Control package. New this year, the accessory is particularly suited to the TC engine but is also available on any Olds V-8 - 2-barrel or 4-barrel. What it does is pipe beat from the right exhaust manifold to a special air cleaner box atop the carburetor.

PHOTOS BY GERRY STILES BOB D`OLIVO

Simulated wire wheel covers on 4-4-2 do best job of cooling optional front disc brakes.

page 54 MOTOR TREND/ FEBRUARY 1967